// $Id$
/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-16 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the
                    Eclipse Public License Version 1.0.

A copy of this license is included in the COPYING file of this distribution.
Please visit http://www.coin-or.org/CppAD/ for information on other licenses.
-------------------------------------------------------------------------- */
/*
$begin atomic_set_sparsity.cpp$$
$spell
	enum
$$

$section Atomic Sparsity with Set Patterns: Example and Test$$

$head function$$
For this example, the atomic function
$latex f : \B{R}^3 \rightarrow \B{R}^2$$ is defined by
$latex \[
f( x ) = \left( \begin{array}{c}
	x_2 \\
	x_0 * x_1
\end{array} \right)
\] $$

$head set_sparsity_enum$$
This example only uses set sparsity patterns.

$nospell

$head Start Class Definition$$
$srccode%cpp% */
# include <cppad/cppad.hpp>
namespace {   // isolate items below to this file
using   CppAD::vector;                          // vector
typedef vector< std::set<size_t> > set_vector;  // atomic_sparsity
//
// a utility to compute the union of two sets.
using CppAD::set_union;
//
class atomic_set_sparsity : public CppAD::atomic_base<double> {
/* %$$
$head Constructor $$
$srccode%cpp% */
public:
	// constructor
	atomic_set_sparsity(const std::string& name) :
	// this exampel only uses set sparsity patterns
	CppAD::atomic_base<double>(name, set_sparsity_enum )
	{ }
private:
/* %$$
$head forward$$
$srccode%cpp% */
	// forward
	virtual bool forward(
		size_t                    p ,
		size_t                    q ,
		const vector<bool>&      vx ,
		vector<bool>&            vy ,
		const vector<double>&    tx ,
		vector<double>&          ty
	)
	{
		size_t n = tx.size() / (q + 1);
# ifndef NDEBUG
		size_t m = ty.size() / (q + 1);
# endif
		assert( n == 3 );
		assert( m == 2 );

		// only order zero
		bool ok = q == 0;
		if( ! ok )
			return ok;

		// check for defining variable information
		if( vx.size() > 0 )
		{	ok   &= vx.size() == n;
			vy[0] = vx[2];
			vy[1] = vx[0] || vx[1];
		}

		// Order zero forward mode.
		// y[0] = x[2], y[1] = x[0] * x[1]
		if( p <= 0 )
		{	ty[0] = tx[2];
			ty[1] = tx[0] * tx[1];
		}
		return ok;
	}
/* %$$
$head for_sparse_jac$$
$srccode%cpp% */
	// for_sparse_jac
	virtual bool for_sparse_jac(
		size_t                          p ,
		const set_vector&               r ,
		set_vector&                     s ,
		const vector<double>&           x )
	{	// This function needed if using f.ForSparseJac
# ifndef NDEBUG
		size_t n = r.size();
		size_t m = s.size();
# endif
		assert( n == x.size() );
		assert( n == 3 );
		assert( m == 2 );

		// sparsity for S(x) = f'(x) * R  = [ 0,   0, 1 ] * R
		s[0] = r[2];
		// s[1] = union(r[0], r[1])
		s[1] = set_union(r[0], r[1]);
		//
		return true;
	}
/* %$$
$head rev_sparse_jac$$
$srccode%cpp% */
	virtual bool rev_sparse_jac(
		size_t                                p  ,
		const set_vector&                     rt ,
		set_vector&                           st ,
		const vector<double>&                 x  )
	{	// This function needed if using RevSparseJac or optimize
# ifndef NDEBUG
		size_t n = st.size();
		size_t m = rt.size();
# endif
		assert( n == x.size() );
		assert( n == 3 );
		assert( m == 2 );

		//                                       [ 0, x1 ]
		// sparsity for S(x)^T = f'(x)^T * R^T = [ 0, x0 ] * R^T
		//                                       [ 1, 0  ]
		st[0] = rt[1];
		st[1] = rt[1];
		st[2] = rt[0];
		return true;
	}
/* %$$
$head for_sparse_hes$$
$srccode%cpp% */
	virtual bool for_sparse_hes(
		const vector<bool>&                   vx,
		const vector<bool>&                   r ,
		const vector<bool>&                   s ,
		set_vector&                           h ,
		const vector<double>&                 x )
	{
		size_t n = r.size();
# ifndef NDEBUG
		size_t m = s.size();
# endif
		assert( x.size() == n );
		assert( h.size() == n );
		assert( n == 3 );
		assert( m == 2 );

		// initialize h as empty
		for(size_t i = 0; i < n; i++)
			h[i].clear();

		// only f_1 has a non-zero hessian
		if( ! s[1] )
			return true;

		// only the cross term between x[0] and x[1] is non-zero
		if( ! ( r[0] & r[1] ) )
			return true;

		// set the possibly non-zero terms in the hessian
		h[0].insert(1);
		h[1].insert(0);

		return true;
	}
/* %$$
$head rev_sparse_hes$$
$srccode%cpp% */
	virtual bool rev_sparse_hes(
		const vector<bool>&                   vx,
		const vector<bool>&                   s ,
		vector<bool>&                         t ,
		size_t                                p ,
		const set_vector&                     r ,
		const set_vector&                     u ,
		set_vector&                           v ,
		const vector<double>&                 x )
	{	// This function needed if using RevSparseHes
# ifndef NDEBUG
		size_t m = s.size();
		size_t n = t.size();
# endif
		assert( x.size() == n );
		assert( r.size() == n );
		assert( u.size() == m );
		assert( v.size() == n );
		assert( n == 3 );
		assert( m == 2 );

		// sparsity for T(x) = S(x) * f'(x) = S(x) * [  0,  0,  1 ]
		//                                           [ x1, x0,  0 ]
		t[0] = s[1];
		t[1] = s[1];
		t[2] = s[0];

		// V(x) = f'(x)^T * g''(y) * f'(x) * R  +  g'(y) * f''(x) * R
		// U(x) = g''(y) * f'(x) * R
		// S(x) = g'(y)

		//                                      [ 0, x1 ]
		// sparsity for W(x) = f'(x)^T * U(x) = [ 0, x0 ] * U(x)
		//                                      [ 1, 0  ]
		v[0] = u[1];
		v[1] = u[1];
		v[2] = u[0];
		//
		//                                      [ 0, 1, 0 ]
		// sparsity for V(x) = W(x) + S_1 (x) * [ 1, 0, 0 ] * R
		//                                      [ 0, 0, 0 ]
		if( s[1] )
		{	// v[0] = union( v[0], r[1] )
			v[0] = set_union(v[0], r[1]);
			// v[1] = union( v[1], r[0] )
			v[1] = set_union(v[1], r[0]);
		}
		return true;
	}
/* %$$
$head End Class Definition$$
$srccode%cpp% */
}; // End of atomic_set_sparsity class
}  // End empty namespace

/* %$$
$head Test Atomic Function$$
$srccode%cpp% */
bool set_sparsity(void)
{	bool ok = true;
	using CppAD::AD;
	using CppAD::NearEqual;
	double eps = 10. * std::numeric_limits<double>::epsilon();
/* %$$
$subhead Constructor$$
$srccode%cpp% */
	// Create the atomic get_started object
	atomic_set_sparsity afun("atomic_set_sparsity");
/* %$$
$subhead Recording$$
$srccode%cpp% */
	size_t n = 3;
	size_t m = 2;
	vector< AD<double> > ax(n), ay(m);
	for(size_t j = 0; j < n; j++)
		ax[j] = double(j + 1);

	// declare independent variables and start tape recording
	CppAD::Independent(ax);

	// call user function
	afun(ax, ay);

	// create f: x -> y and stop tape recording
	CppAD::ADFun<double> f;
	f.Dependent (ax, ay);  // f(x) = x

	// check function value
	ok &= NearEqual(ay[0] , ax[2],  eps, eps);
	ok &= NearEqual(ay[1] , ax[0] * ax[1],  eps, eps);

/* %$$
$subhead for_sparse_jac$$
$srccode%cpp% */
	// correct Jacobian result
	set_vector check_s(m);
	check_s[0].insert(2);
	check_s[1].insert(0);
	check_s[1].insert(1);
	// compute and test forward mode
	{	set_vector r(n), s(m);
		for(size_t i = 0; i < n; i++)
			r[i].insert(i);
		s = f.ForSparseJac(n, r);
		for(size_t i = 0; i < m; i++)
			ok &= s[i] == check_s[i];
	}
/* %$$
$subhead rev_sparse_jac$$
$srccode%cpp% */
	// compute and test reverse mode
	{	set_vector r(m), s(m);
		for(size_t i = 0; i < m; i++)
			r[i].insert(i);
		s = f.RevSparseJac(m, r);
		for(size_t i = 0; i < m; i++)
			ok &= s[i] == check_s[i];
	}
/* %$$
$subhead for_sparse_hes$$
$srccode%cpp% */
	// correct Hessian result
	set_vector check_h(n);
	check_h[0].insert(1);
	check_h[1].insert(0);
	// compute and test forward mode
	{	set_vector r(1), s(1), h(n);
		for(size_t i = 0; i < m; i++)
			s[0].insert(i);
		for(size_t j = 0; j < n; j++)
			r[0].insert(j);
		h = f.ForSparseHes(r, s);
		for(size_t i = 0; i < n; i++)
			ok &= h[i] == check_h[i];
	}
/* %$$
$subhead rev_sparse_hes$$
Note the previous call to $code ForSparseJac$$ above
stored its results in $icode f$$.
$srccode%cpp% */
	// compute and test reverse mode
	{	set_vector s(1), h(n);
		for(size_t i = 0; i < m; i++)
			s[0].insert(i);
		h = f.RevSparseHes(n, s);
		for(size_t i = 0; i < n; i++)
			ok &= h[i] == check_h[i];
	}
/* %$$
$subhead Test Result$$
$srccode%cpp% */
	return ok;
}
/* %$$
$$ $comment end nospell$$
$end
*/
